Combination pressure sensor and regulator for direct injection engine fuel system

ABSTRACT

A pressure regulating device for high pressure fuel systems includes a pressure sensing element attached directly to a pressure chamber. The pressure sensing element includes a semiconductor element that deflects in response to a deflection of a portion of the pressure caused by fuel pressure within the pressure chamber. A coil is electrically connected with the pressure sensing element and is configured to generate a magnetic field that moves a magnetic armature to control fuel pressure.

RELATED APPLICATION

This application is a Divisional application of pending U.S. patentapplication Ser. No. 09/376,823 filed Aug. 18, 1999.

FIELD OF THE INVENTION

The present invention relates generally to pressure regulating devicesand, more particularly, to pressure regulating devices for fuel systems.

BACKGROUND OF THE INVENTION

To help meet consumer demand for more fuel efficient vehicles,automotive companies have begun investigating the use of directinjection fuel systems for internal combustion engines. In a directinjection fuel system, a fuel injector injects highly pressurized fueldirectly into an engine cylinder combustion chamber during thecompression stroke. Direct fuel injection can facilitate efficient fuelcombustion, thereby improving fuel economy.

Because fuel is injected during a compression stroke, the fuel must beat a high pressure (e.g., about 200 Bar or 2,900 psi) in order to enterthe cylinder. High fuel pressure is typically achieved by using ahigh-pressure booster pump in conjunction with a low pressure fuel tankpump.

FIG. 1 is a schematic illustration of a conventional direct injectionfuel system 5 for an internal combustion engine. Fuel, such as gasoline,is pumped from a tank 10 via a low pressure tank pump 12 to a highpressure booster pump 14. The high pressure booster pump 14 raises thepressure of the fuel so that the fuel can enter a combustion chamberagainst the compression pressure in the cylinder. Typically, a highpressure booster pump is mounted to an engine and is operated directlyfrom a cam (or crank) shaft within the engine. As illustrated in FIG. 1,the high pressure fuel discharged from the high pressure booster pump 14flows through a fuel rail 42 and to each injector 18 via a respectivefuel passageway 20. Each injector 18 is configured to deliver acontrolled amount of fuel into a respective cylinder 22 when activatedby an engine control unit (ECU) 24. Conventionally, fuel pressure in afuel rail 42 is controlled via a fuel rail pressure regulator 26 and afuel rail pressure sensor 28. Typically, the pressure sensor 28 andpressure regulator 26 communicate with each other via an ECU 24.

Because two separate components (i.e., a pressure regulator and apressure sensor) are typically used to control fuel pressure inconventional direct injection fuel systems, multiple connections in afuel rail are typically necessary. Unfortunately, each connection in ahigh pressure fuel rail is a potential source of fuel leakage. Becausefuel rails are typically mounted near hot exhaust manifolds, thepotential for fire caused by a fuel leak from a high pressure fuel railcan be substantial.

SUMMARY OF THE INVENTION

In view of the above discussion, it is an object of the presentinvention to facilitate reducing the potential for fire caused by fuelleaks in high pressure direct injection fuel systems for internalcombustion engines.

It is another object of the present invention to provide fuel pressuremonitoring and control for high pressure direct injection fuel systemswherein only a single connection in a fuel rail is required.

These and other objects of the present invention are provided bypressure regulating devices for high pressure fluid systems, such asfuel systems, wherein a pressure sensing element is attached directly toa pressure chamber within a pressure regulating device. According to oneembodiment of the present invention, a sense tube assembly is disposedwithin an axial bore of a housing. The sense tube assembly includes alongitudinally extending outer tube having a longitudinally extendinginner tube disposed within the outer tube to define a fuel pressurechamber.

The outer tube has a tubular body terminating at an open end and at anopposite closed end. A longitudinally extending channel is formed alongthe inner surface of the outer tube body from the outer tube open endtoward the outer tube closed end.

The inner tube has a tubular body terminating at an open end and at anopposite closed end. The inner tube closed end includes an apertureformed therethrough. A radially extending flange is positioned adjacentthe inner tube open end and has an aperture formed through a portionthereof. The longitudinally extending channel in the outer tube is influid communication with a fuel inlet passageway in the housing via theflange aperture. The longitudinally extending channel in the outer tubeforms a fuel flow path between the inner tube and the outer tube fromthe fuel inlet passageway to the fuel pressure chamber.

A magnetic pole piece is disposed within the inner tube and includesopposite first and second ends and an internal bore that terminates atthe magnetic pole piece first and second ends. The magnetic pole pieceinternal bore is in fluid communication with a fuel outlet passageway inthe housing.

A magnetic armature is slidably secured within the inner tube betweenthe magnetic pole piece and the inner tube closed end. The magneticarmature includes a body having a pair of slots formed in the outersurface thereof and terminating at opposite first and second ends. Themagnetic armature second end is configured to matingly engage theaperture in the inner tube closed end. The slots formed in the armatureare in fluid communication with the magnetic pole piece internal bore. Aspring, located between the magnetic armature and magnetic pole piece,is configured to bias the magnetic armature away from the magnetic polepiece and to cause the magnetic armature second end to matingly engagethe aperture in the inner tube closed end.

A pressure sensing element is attached to the outer tube closed end andis configured to measure fuel pressure within the pressure chamber. Thepressure sensing element includes a semiconductor element that deflectsin response to a deflection of the outer tube second end caused bypressure within the pressure chamber. A coil disposed within the housingis electrically connected with the pressure sensing element and isconfigured to generate a magnetic field responsive to electrical signalsfrom the pressure sensing element. The magnetic field moves the magneticarmature axially within the inner tube to control fuel pressure byallowing fuel entering the pressure chamber via the fuel inletpassageway to exit via a fuel outlet passageway.

Because the present invention combines a pressure sensing element andpressure regulator within a single device, only a single connection in afuel rail is required. Accordingly, the number of potential sources offuel leaks is reduced by the present invention.

According to another embodiment of the present invention, a controller,such as a proportional-integral-derivative (PID) controller, may beelectrically connected with the pressure sensing element to create a“smart solenoid” whereby fuel pressure can be maintained within aprescribed range of pressures. The controller closes the loop around thesensed pressure via the pressure sensing element and adjusts the voltageto the coil which controls the axial movement of the magnetic armaturewithin the inner tube in order to maintain fuel pressure within apredetermined range.

According to another embodiment of the present invention, apost-assembly calibration method is provided to compensate formechanical strain imposed on pressure sensing elements during assemblyof pressure regulating devices. A pressure sensing element attached to apressure chamber within a pressure regulating device housing iselectrically connected to an electrical terminal located external to thehousing. The pressure sensing element is then calibrated to compensatefor mechanical strain imposed on the pressure sensing element duringassembly by transmitting electrical signals to the pressure sensingelement via the electrical terminal.

The present invention may be utilized with various high pressure fluidsystems, and is not limited to high pressure fuel systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a conventional direct injectionfuel system for an internal combustion engine.

FIG. 2 is a side, section view of a fuel pressure regulating apparatusaccording to an embodiment of the present invention.

FIG. 3A is a side, section view of the inner tube of the sense tubeassembly within the pressure regulating apparatus of FIG. 2.

FIG. 3B is an end view of the inner tube of FIG. 3A illustrating anaperture formed in the flange that permits fuel to flow from the fuelinlet passageway into the fuel flow path between the inner tube and theouter tube.

FIG. 4A is a side, section view of the outer tube of the sense tubeassembly within the pressure regulating apparatus of FIG. 2.

FIG. 4B is a section view of the outer tube of FIG. 4A illustrating alongitudinally extending channel which forms a fuel flow path betweenthe inner tube and outer tube of the sense tube assembly.

FIG. 5A is an enlarged section view of the magnetic armature in thepressure regulating apparatus of FIG. 2.

FIG. 5B is an enlarged end view of the magnetic armature of FIG. 5Ataken along lines 5B—5B.

FIG. 6A is an enlarged section view of the magnetic pole piece in thepressure regulating apparatus of FIG. 2.

FIG. 6B is an enlarged end view of the magnetic pole piece of FIG. 6Ataken along lines 6B—6B.

FIG. 7 is an enlarged side, section view of the pressure regulatingapparatus of FIG. 2 illustrating the pressure sensing element that isattached to the outer surface of the outer tube second end.

FIG. 8 is a bottom plan view of the electrical connector socket of thepressure regulating apparatus of FIG. 2 illustrating the electricalterminals contained therein.

FIG. 9 is a schematic illustration of operations for calibrating apressure sensing element within a pressure regulating apparatusaccording to the present invention to compensate for mechanical strainimposed on the pressure sensing element during assembly.

FIG. 10 is a schematic illustration of a direct injection fuel systemincorporating various aspects of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

Referring now to FIG. 2, a pressure regulating apparatus 40 according toan embodiment of the present invention is illustrated. The pressureregulating apparatus 40, which is in fluid communication with a fuelrail 42, includes an annular first housing portion 43 and an annularmagnetic flux housing 44 which are collectively referred to herein as a“housing” that has an axial bore 45 extending therethrough. The axialbore 45 defines a longitudinally extending axial direction, indicated byreference letter A, and is configured to receive a flow plug 46, sensetube assembly 47 and pressure sensing element 48 as will be described indetail below.

The illustrated fuel rail 42 includes a first end portion 42 a that isconfigured to receive an end portion 46 a of a flow plug 46. In theillustrated embodiment, a filter 17 is attached to the flow plug endportion 46 a to prevent foreign materials entrained within fuel fromentering the pressure regulating apparatus 40. The fuel rail 42 is influid communication with a fuel inlet passageway 54 a and a fuel outletpassageway 54 b in the flow plug 46.

The illustrated fuel rail 42 also includes a second end portion 42 bthat is threadingly engaged with a first end portion 43 a of the annularfirst housing portion 43. An O-ring 49 is configured to maintain asealed engagement between the fuel rail 42 and the annular first housingportion 43 as would be understood by one skilled in the art.

The annular flux housing 44 has opposite first and second end portions44 a, 44 b. The annular flux housing 44 is configured to enclose aninsulating bobbin 50 disposed therewithin and having conductive wire 51coiled therearound to define a coil 52 for generating a magnetic fieldwhen electrical current flow is induced therein. The coil 52 generates amagnetic field which causes magnetic flux to flow through the fluxhousing 44, into the upper flux washer 55, into a magnetic armature 80,into a magnetic pole piece 84, into a lower flux washer 56, and thenback to the flux housing 44. The flow of magnetic flux causes themagnetic armature 80 to move axially within the sense tube assembly 47.This magnetic force is assisted by the fuel pressure force pushing onthe magnetic armature 80 at the poppet seat 72. Opposing these twoforces is the force of the armature spring 82. The balancing of theseforces is what allows for pressure regulation of fuel within the fuelrail 42. Coils for moving magnetic armatures (or solenoids) are wellunderstood by those skilled in this art and need not be describedfurther herein.

The flow plug 46 is positioned within the axial bore 45 as illustrated.The flow plug 46 has a first end 46 a secured within the fuel rail 42.The flow plug 46 includes a fuel inlet passageway 54 a and a fuel outletpassageway 54 b. The fuel inlet passageway 54 a is in fluidcommunication with the fuel rail 42. The flow plug 46 has an oppositesecond end portion 46 b secured within an inner tube 60 of the sensetube assembly 47. An O-ring 53 a is configured to prevent fuel leakagebetween the flow plug first end 46 a and the fuel rail 42, and an O-ring53 b is configured to prevent fuel leakage between the flow plug secondend 46 b and the inner tube 60 as would be understood by one skilled inthe art. Fuel enters the pressure regulating apparatus 40 from the fuelrail 42 via the fuel inlet passageway 54 a and exits from the pressureregulating apparatus 40 via the fuel outlet passageway 54 b, as will bedescribed in detail below.

The illustrated sense tube assembly 47 disposed within the axial bore 45includes a longitudinally extending inner tube 60 disposed within alongitudinally extending outer tube 66. The inner tube 60 and outer tube66 will now be described in with reference to FIGS. 3A-3B and FIGS.4A-4B, respectively.

Referring to FIG. 3A, a side, section view of the inner tube 60 isillustrated. The illustrated inner tube 60 includes a tubular(preferably cylindrical) body 61 a with an open end 61b and a closed end61 c, and inner and outer surfaces 61 d, 61 e. The inner tube 60 definesan elongated, cylindrical chamber 64 extending between the open andclosed ends 61 b, 61 c that is configured to receive the magneticarmature 80 and a pole piece 84 as described below.

The inner tube closed end 61 c has an annular configuration that definesan aperture 71. As will be described below, the aperture 71 defines apoppet seat 72 for receiving the armature first end 80 a (FIG. 2) inmating relationship. A radially extending flange 62 is positionedadjacent the inner tube open end 61 b, as illustrated. An aperture 63 isformed through a portion of the flange 62, as illustrated. FIG. 3B is anend view of the inner tube 60 illustrating the flange 62 and theaperture 63 formed therein.

Referring to FIG. 4A, a side, section view of the outer tube 66 isillustrated. The outer tube 66 includes a tubular body 67 a having anopen end 67 b and an opposite closed end 67 c, and having inner andouter surfaces 67 d, 67 e. A longitudinally extending channel 68 isformed along the inner surface 67 d of the outer tube body 67 a from theouter tube open end 67 b toward the outer tube closed end 67 c. FIG. 4Bis a section view of the outer tube 62 that illustrates thecross-sectional contour of the longitudinally extending channel 68.

The outer tube 66 defines an elongated, cylindrical chamber 70 extendingbetween the open and closed ends 67 b, 67 c that is configured toreceive the inner tube 60 therewithin. The outer tube open end 67 bincludes a radially extending flange 74 adjacent thereto as illustrated.The flange 74 abuts the flange 62 of the inner tube 60 when the innertube 60 is assembled within the outer tube chamber 70 (as illustrated inFIG. 2).

The outer tube second end 67 c has an outer surface 75 to which thepressure sensing element 48 (FIG. 2) is attached. In the illustratedembodiment, a slot 76 circumferentially extends around the outer tube 66adjacent the second end 67 c as illustrated in FIG. 4A. The slot 76 isconfigured to receive an O-ring (77, FIG. 2) that is configured to sealthe outer tube 66 within the axial bore 45 as would be understood by oneskilled in the art.

When the inner and outer tubes 60, 66 are assembled to form the sensetube assembly 47, the outer surface 61 e of the inner tube body 61 a isin contacting relationship with the inner surface 67 d of the outer tubebody 67 a to define a pressure chamber 65 between the outer tube closedend and the inner tube closed end, as illustrated in FIG. 2. The fitbetween the inner tube 60 and the outer tube 62 is sufficiently snugsuch that fuel within a pressure range of between about 0 pounds persquare inch (psi) and about 3,000 psi is prevented from leakingtherebetween.

Preferably, the inner tube 60 is formed from non-magnetic materialincluding, but not limited to, non-magnetic stainless steel having athickness of between about 0.012 inches and about 0.018 inches.Preferably, the outer tube 66 is formed from non-magnetic materialincluding, but not limited to, non-magnetic stainless steel having athickness of between about 0.012 inches and about 0.018 inches.

In addition, the longitudinally extending channel 68 in the outer tube66 forms a fuel flow path 69 located between the inner tube 60 and theouter tube 66. The aperture 63 in the inner tube flange 62 is alignedwith an annular ring on the outer tube. This annular ring creates acavity 67 e which feeds the fuel flow path 69 so that the fuel inletpassageway 54 a is in fluid communication with the fuel flow path 69.Accordingly, fuel can flow from the fuel inlet passageway 54 a into thepressure chamber 65 via the fuel flow path 69.

Referring back to FIG. 2, the magnetic armature 80, a spring 82 and themagnetic pole piece 84 are disposed within the inner tube chamber 64, asillustrated. The magnetic armature 80 includes opposite first and secondends 80 a, 80 b and is slidably secured within the inner tube chamber64. The magnetic armature 80 is configured to move along the axialdirection A in response to a magnetic field generated by the coil 52.The magnetic pole piece 84 is fixed within the inner tube chamber 64adjacent the magnetic armature first end 80 a and includes oppositefirst and second ends 84 a, 84 b, as illustrated.

The magnetic armature 80 is biased via the spring 82 along the axialdirection A away from the pole piece second end 84 b and toward theinner tube second end 61 c. The magnetic armature second end 80 b isconfigured to matingly engage with the poppet seat 72 formed in theinner tube second end 61 c to prevent passage of fuel into the innertube chamber 64. In the illustrated embodiment, the magnetic armature 80is mechanically loaded to a closed position when current is not inducedwithin the coil 52. However, it is understood that the magnetic armature80 may be mechanically loaded to an open position via the spring 82 whencurrent is not induced within the coil 52.

Still referring to FIG. 2, the magnetic pole piece 84 includes an axialbore 85 extending along the axial direction A between the opposite firstand second ends 84 a, 84 b, as illustrated. A portion of the magneticpole piece axial bore adjacent the pole piece second end 84 a isthreaded and configured to receive a correspondingly-threaded adjustingscrew 86 therein as illustrated. The adjusting screw 86 is configured toadjust or calibrate the position of the magnetic armature second end 80b with respect to the poppet seat 72 at the inner tube second end 61 cby compressing or expanding the spring 82, as would be understood by oneof skill in the art.

The annular flux housing 44, magnetic armature 80, upper and lower fluxwashers 55, 56 and magnetic pole piece 84 form a magnetic flux circuitsuch that flow of electrical current within the coil 52 produces amagnetic field that causes the magnetic armature first end 80 a to movein the axial direction A within the inner tube 60 toward the pole piecesecond end 84 b. The spring 82 biases against the magnetic armaturefirst end 80 a to counter the magnetic force attracting the magneticarmature 80 towards the pole piece 84. As would be understood by one ofskill in the art, the amount of movement of the magnetic armature 80 maybe controlled by controlling the amount of electrical current applied tothe coil 52 and/or by selecting a spring that has a desired spring rate.Fuel pressure exerted on the magnetic armature is typically betweenabout 0 psi and about 1,500 psi.

Referring now to FIGS. 5A-5B, the configuration of the magnetic armature80 illustrated in FIG. 2 is shown in enlarged detail. The second end 80b has a conical-shaped projection 80 c that is configured to matinglyengage with the poppet seat 72 formed in the inner tube second end 61 c.The magnetic armature 80 includes a pair of diametrically opposed slots88 a, 88 c that extend between the opposite first and second ends 80 a,80 b. Slots 88 a, 88 c allow fuel passing through the inner tubeaperture 71 from the pressure chamber 65 to flow past the magneticarmature 80 and into the axial bore 85 of the magnetic pole piece 84. Itis understood that the magnetic armature 80 may have various shapes andconfigurations and is not limited to the illustrated embodiment. Forexample, the magnetic armature 80 may have a “D” shape (in lieu of slots88 a, 88 c) which allows fuel to flow past the magnetic armature 80 andinto the axial bore 85 of the magnetic pole piece 84.

The magnetic armature 80 also includes a bore 89 that extends partiallyinto the magnetic armature from the first end 80 a. The bore 89 isconfigured to receive the spring (82, FIG. 2) therein for biasing themagnetic armature away from the magnetic pole piece second end 84 b.

Referring now to FIGS. 6A-6B, the configuration of the magnetic polepiece 84 illustrated in FIG. 2 is shown in enlarged detail. The magneticpole piece 84 includes the axial bore 85 and a pair of diametricallyopposed slots 90 a, 90 b that extend between opposite first and secondends 84 a, 84 b. The slots 90 a, 90 b are in communication with theaxial bore 85. The slots 84 a, 84 b and the axial bore 85 allow fuelflowing around the magnetic armature 80 to flow through the magneticpole piece and into a chamber 92 within the flow plug 46 that is influid communication with the fuel outlet passageway 54 b.

Referring back to FIG. 2, an air gap shim 87 is positioned between themagnetic armature 80 and the magnetic pole piece 84 as illustrated. Theair gap shim 87 is formed from non-magnetic material and preventsmagnetic “latch” from occurring between the magnetic armature 80 and themagnetic pole piece 84, as would be understood by one of skill in theart.

Referring now to FIG. 7, the pressure sensing element 48 that is mounteddirectly to the outer surface 75 of the second end 67 c of the outertube 66 is illustrated in enlarged detail. The pressure sensing element48 preferably includes a semiconductor element 100 having an embeddedresistive element such as a Wheatstone bridge. The semiconductor element100 is preferably a planar substrate formed from silicon. However, thesemiconductor element 100 may have various configurations and may beformed from various materials. In the illustrated embodiment, thesemiconductor element 100 is surrounded by a protective covering or diecap 101.

As fuel pressure increases within the pressure chamber 65 (indicated byarrows P), the second end 67 c of the outer tube 66 deflects toward thesemiconductor element 100. The deflection of the second end 67 c of theouter tube 66 causes the semiconductor element 100 to deflect whichchanges its resistance.

By applying a known voltage to the pressure sensing element 48 andmonitoring the voltage drops across the pressure sensing element 48,changes can be detected. By applying a plurality of known pressures tothe sense surface (i.e., the outer surface 75 of the second end 67 c ofthe outer tube 66) and monitoring the voltage changes induced on thepressure sensing element 48 by these known pressures, the pressuresensing element 48 can be accurately calibrated to produce a pressuretransducer.

As would be understood by one of skill in the art, electrical resistivestrain devices produce a varying resistance when strained by amechanical force. Accordingly, deflection of the second end 67 c of theouter tube 66 causes the semiconductor element 100 to deflect and, thus,change resistance. By supplying a voltage to the semiconductor element100, a sensed voltage that is proportional to the amount of fuelpressure within the pressure chamber 65 can be generated. An exemplarypressure sensing element 48 is disclosed in co-pending and co-assignedU.S. patent application Ser. No. 08/840,363, filed Apr. 28, 1997, whichis incorporated herein by reference in its entirety.

A flex circuit assembly 102 that includes electronics to supply theresistive bridge with voltage and process the voltage signals of thesemiconductor element 100 is electrically connected to the semiconductorelement 100 via lead 102 a. Lead 102 b electrically connects the flexcircuit assembly 102 to an electrical terminal 110 a. Electricalterminal 110 a is preferably electrically connected with an ECU (24,FIG. 1) via an electrical cable inserted within the socket 114. In theillustrated embodiment, the flex circuit assembly 102 is embedded withina dielectric material 103 such as KAPTON® flexible film (E. I. du Pontde Nemours and Company, 1007 Market St., Wilmington, Del.). Flexibledielectric films are well known by those having skill in the art andneed not be described further herein.

The output from the pressure sensing element 48 is typically a 0.0-5.0volt direct current (DC) analog signal. However, the output from thepressure sensing element 48 may also be a digital data stream. Theoutput from the pressure sensing element 48 is preferably generatedinternally via an application specific integrated circuit (ASIC) whichhas a processor built therein. The processor takes a voltage readingfrom the semiconductor element 100 and a voltage reading that isproportional to temperature and generates the output voltage.

The flex circuit assembly 102 preferably includes a static groundprotection system and an electromagnetic interference (EMI) circuit todampen out background radiation. Static ground protection systems andEMI circuits are well known by those of skill in the art and need not bedescribed further herein.

Preferably, additional terminals 110 b-110 e are housed within thesocket 114, as illustrated in FIG. 8. As would be understood by one ofskill in the art, terminals 110 b-110 e may be provided to performvarious functions, including: providing electrical power to the coil 52;providing ground; providing an output line from the pressure sensingelement 48; providing power to the pressure sensing element 48; andproviding ground.

Pressure Sensing Element Calibration

Prior to final assembly of the pressure regulating apparatus 40, theelectronic pressure sensing element 48 is typically calibrated. However,assembly of the pressure regulating apparatus 40 may induce mechanicalstrain on the outer tube 66 and/or the pressure sensing element 48 whichmay, in turn, negatively affect any pre-assembly calibration efforts.According to another embodiment of the present invention, calibration ofa pressure sensing element housed within a pressure regulating apparatuscan be performed after assembly is complete.

Referring now to FIG. 9, operations for calibrating a pressure sensingelement within a pressure regulating apparatus to compensate formechanical strain imposed on the pressure sensing element duringassembly of the pressure regulating apparatus are illustrated. Apressure chamber and pressure sensing element attached thereto isenclosed within a housing, such that the pressure sensing element iselectrically connected to an electrical terminal located external to thehousing (Block 200). Electrical signals generated by the pressuresensing element are detected via the electrical terminal (Block 202).Finally, the pressure sensing element is then calibrated to compensatefor mechanical strain imposed thereon during assembly by transmittingelectrical signals to the pressure sensing element via the electricalterminal (Block 204).

Because actual changes in voltage generated by the pressure sensingelement 48 are small, temperature can play an important role incalibration of the pressure sensing element 48. Calibration ispreferably performed by applying known pressures to the pressure sensingelement 48 while the pressure sensing element 48 is at differenttemperatures and then monitoring the voltage signals produced by thepressure sensing element 48. The output signal from the pressure sensingelement 48 can then be adjusted.

Preferably, an electrical terminal for transmitting the output signalfrom the pressure sensing element 48 is utilized as a digitalinput/output (I/O) port to program the ASIC. The ASIC has a monitoringcircuit that checks the electrical terminal for digital communications.The electrical terminal thus allows the pressure sensing element 48 tobe calibrated after the pressure regulating apparatus 40 has beenassembled. By contrast, calibration of conventional pressure sensors isperformed prior to final assembly.

Direct Injection Fuel System

Referring now to FIG. 10, a direct injection fuel system 5′ for aninternal combustion engine incorporating a pressure regulating apparatusaccording to various aspects of the present invention is schematicallyillustrated. The illustrated direct injection fuel system 5′ includes afuel tank 10, a fuel rail 42, and a fuel supply line 17 connecting thefuel tank 10 and the fuel rail 42. A high pressure booster pump 14 isprovided for pumping fuel from the fuel tank 10 to the fuel rail 42 viathe fuel supply line 17. As described above with respect to FIG. 1, alow pressure fuel pump 12 may also be utilized, as would be understoodby one skilled in the art. A plurality of fuel injectors 18 are in fluidcommunication with the fuel rail 42 and each fuel injector 18 isconfigured to directly inject fuel from the fuel rail 42 into arespective combustion chamber 22 within the internal combustion engine.

A pressure regulating apparatus 40 as described above is in fluidcommunication with the fuel rail 42. A fuel return line 19 connects thepressure regulating apparatus 40 and the fuel tank 10 and is configuredto return fuel exiting from the pressure regulating apparatus 40 to thefuel tank.

As will be described below, a controller 30 may be electricallyconnected with a pressure sensing element within the pressure regulatingapparatus 40 and configured to maintain fuel pressure within aprescribed range of pressures based upon the requested input. Thecontroller 30 may be a proportional controller, a derivative controller,an integral controller, or some combination thereof. For example, thecontroller 30 may be a proportional-derivative controller, aproportional-integral controller, or a proportional-integral-derivative(PID) controller. Each of the above-mentioned types of controllers arewell known to those skilled in the art and need not be described furtherherein.

Pressure Regulating Apparatus Operation

Referring back to FIG. 2, operation of the illustrated pressureregulating apparatus 40 will now be described. High pressure fuel entersthe pressure regulating apparatus 40 from the fuel rail 42 through thefuel inlet passageway 54 a in the flow plug 46. The fuel passes throughthe aperture 63 in the flange 62 of the inner tube 60 and into the fuelflow path 69 between the inner and outer tubes 60, 66. The fuel flowsthrough the fuel flow path 69 and into the pressure chamber 65 betweenthe outer tube closed end 67 c and the inner tube closed end 61 c.

Fuel pressure within the pressure chamber 65 causes the outer tubeclosed end 67 c to deflect, which in turn causes the semiconductorelement 100 within the pressure sensing element 48 to deflect. As wouldbe understood by one of skill in the art, the resistance in theWheatstone bridge embedded within the semiconductor element 100 changeswith the deflection (strain) in the strain in the semiconductor element100 to produce an output voltage when a constant current is applied viaterminal 110 a. The output voltage is proportional to the deflection ofthe semiconductor element 100 which is proportional to the fuel pressurein pressure chamber 65. As would be understood by one of skill in theart, the fuel pressure measured in the pressure chamber 65 will be thesame as the fuel pressure within the fuel rail 42.

The pressure sensing element 48 reports fuel pressure in the fuel rail42 back to the vehicle ECU (24, FIG. 10). The pressurized fuel alsoexerts positive pressure against the magnetic armature second end 80 bthrough aperture 71 in the inner tube second end 61 c.

To regulate fuel pressure within the fuel rail 42, a vehicle ECU readsthe fuel pressure output signal from the pressure sensing element 48 anddetermines what the proper fuel pressure should be based upon variousvehicle parameters including, but not limited to, throttle position,engine speed (RPM), transmission gear, and wheel slip. The ECU checks tosee if the fuel pressure is where it should be, and if not, adjusts thesignal to the pressure regulating apparatus 40 to change the fuelpressure to the desired level. As described above, fuel pressure isadjusted by applying electrical current to the coil 52. The generatedmagnetic field causes the magnetic armature 80 to move along the axialdirection A toward the magnetic pole piece 84, which opens a leak pathback to the fuel tank (10, FIG. 10) in the vehicle, thereby reducingfuel pressure in the fuel rail 42. The leak path is formed by the slots88 a, 88 c in the magnetic armature 80, the axial bore 85 through themagnetic pole piece 84, the chamber 92 within the flow plug 46, the fueloutlet passageway 54 b in the flow plug 46, and the fuel outletpassageway 99 in the annular first housing 42.

The pressure regulating apparatus 40 can also act as a pressure reliefvalve if fuel pressure exceeds a predetermined pressure limit. Excessivefuel pressure applied to the magnetic armature second end 80 b can causethe spring 82 to compress, which will allow flow through the leak pathand, thus, a reduction in fuel pressure.

According to another embodiment of the present invention, the controller(30, FIG. 10) may be electrically connected with a pressure sensingelement 48 to create a “smart solenoid”(i.e., a closed loop feedbackcontrol system is incorporated into the pressure sensing electronics),whereby fuel pressure can be maintained within a prescribed range ofpressures. The controller 30 closes the loop around the sensed pressurevia the pressure sensing element 48 and adjusts, via current inducedwithin the coil 52, axial movement of the magnetic armature 80 withinthe inner tube 60 in order to maintain fuel pressure within apredetermined range.

By reading the pressure sensing element 48, an ECU is able to see theeffects that its changes are having on fuel pressure and can vary fuelpressure change requests. The control of how much change an ECU asks thepressure sensing element 48 to make and how quickly it should make thatchange is preferably controlled via proportional-integral-derivative(PID) control. A PID controller can allow a system to control the amountof overshoot that a fuel rail sees from the pressure regulatingapparatus 40 and also can help insure that the pressure regulatingapparatus 40 receives the required value quickly.

A pressure regulating apparatus according to the present inventionprovides a number of advantages. First, the number of electricalterminals required by a pressure regulating apparatus according to thepresent invention can be reduced from five to three. Second, the outputsignal line from a pressure regulating apparatus according to thepresent invention can change from analog to digital. Third, a pressureregulating apparatus according to the present invention can house thecontrol electronics (e.g., a FET transistor, resistor, and capacitor)required to drive the coil.

The foregoing is illustrative of the present invention and is not to beconstrued as limiting thereof. Although a few exemplary embodiments ofthis invention have been described, those skilled in the art willreadily appreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe claims. In the claims, means-plus-function clauses are intended tocover the structures described herein as performing the recited functionand not only structural equivalents but also equivalent structures.Therefore, it is to be understood that the foregoing is illustrative ofthe present invention and is not to be construed as limited to thespecific embodiments disclosed, and that modifications to the disclosedembodiments, as well as other embodiments, are intended to be includedwithin the scope of the appended claims. The invention is defined by thefollowing claims, with equivalents of the claims to be included therein.

That which is claimed is:
 1. A direct injection fuel system for aninternal combustion engine, comprising: a fuel tank; a fuel rail; a fuelsupply line connecting the fuel tank and the fuel rail; a pump forpumping fuel from the fuel tank to the fuel rail via the fuel supplyline; a plurality of fuel injectors in fluid communication with the fuelrail, wherein each fuel injector is configured to directly inject fuelfrom the fuel rail into a respective combustion chamber within theinternal combustion engine; a pressure sensing and pressure regulatingunit that senses and regulates fuel pressure within the fuel rail,comprising: a housing; a pressure chamber within the housing comprisinga wall configured to deflect responsive to fuel pressure within thepressure chamber, wherein the pressure chamber is in fluid communicationwith the fuel rail; a pressure sensing device attached to the wallwithin the housing, wherein the pressure sensing device is configured togenerate electrical signals responsive to deflection of the pressurechamber cause by fuel pressure within the pressure chamber; and apressure regulating device within the housing comprising a valve memberthat is configured to relieve fuel pressure in the pressure chamber byallowing fuel to exit from the pressure chamber to the fuel tank,wherein movement of the valve member is responsive to electrical signalsgenerated by the pressure sensing device.
 2. A direct injection fuelsystem according to claim 1 wherein the pressure sensing devicecomprises a semiconductor element.
 3. A direct injection fuel systemaccording to claim 1 wherein the valve member comprises a magneticarmature.
 4. A direct injection fuel system according to claim 3 furthercomprising a coil disposed within the housing, wherein the coil iselectrically connected with the pressure sensing device, and wherein thecoil is configured to generate a magnetic field responsive to electricalsignals from the pressure sensing device that moves the magneticarmature to control fuel pressure within the pressure chamber byallowing fuel to exit from the pressure chamber to the fuel tank.
 5. Adirect injection fuel system according to claim 1 further comprising acontroller electrically connected with the pressure sensing device andconfigured to maintain fuel pressure within the fuel rail within apredetermined range of pressures, and wherein the controller is selectedfrom the group consisting of proportional controllers, derivativecontrollers, integral controllers, proportional-derivative controllers,proportional-integral controllers, and proportional-integral-derivativecontrollers.
 6. A direct injection fuel system for an internalcombustion engine, comprising: a fuel tank; a fuel rail; a fuel supplyline connecting the fuel tank and the fuel rail; a pump for pumping fuelfrom the fuel tank to the fuel rail via the fuel supply line; aplurality of fuel injectors in fluid communication with the fuel rail,wherein each fuel injector is configured to directly inject fuel fromthe fuel rail into a respective combustion chamber within the internalcombustion engine; a pressure regulating apparatus, comprising: ahousing having an axial bore extending therethrough that defines alongitudinal direction, wherein the housing includes a fuel inletpassageway in fluid communication with the fuel rail and a fuel outletpassageway; a sense tube assembly disposed within the axial bore,comprising: a longitudinally extending outer tube, comprising: a tubularbody having an inner surface and an outer surface and having an open endand an opposite closed end; and a longitudinally extending channelformed along the inner surface of the outer tube body from the outertube open end toward the outer tube closed end; and a longitudinallyextending inner tube disposed within the outer tube, comprising: atubular body having an inner surface and an outer surface and having anopen end and an opposite closed end; wherein the inner tube closed endincludes an aperture formed therethrough; wherein the outer surface ofthe inner tube body is in contacting relationship with the inner surfaceof the outer tube body to define a pressure chamber between the outertube closed end and the inner tube closed end; and wherein thelongitudinally extending channel is in fluid communication with the fuelinlet passageway and forms a fuel flow path between the inner tube andthe outer tube from the fuel inlet passageway to the pressure chamber; amagnetic pole piece disposed within the inner tube, comprising: oppositefirst and second ends; and an internal bore that terminates at themagnetic pole piece first and second ends, wherein the internal bore isin fluid communication with the fuel outlet passageway; a magneticarmature slidably secured within the inner tube between the magneticpole piece and the inner tube closed end, comprising: a body having anouter surface and terminating at opposite first and second ends, whereinthe magnetic armature second end is configured to matingly engage theaperture in the inner tube closed end; and a longitudinally extendingpassageway that terminates at the magnetic armature first and secondends and that is in fluid communication with the magnetic pole pieceinternal bore; biasing means configured to bias the magnetic armatureaway from the magnetic pole piece and to cause the magnetic armaturesecond end to matingly engage the aperture in the inner tube closed end;a pressure sensing element attached to the outer tube closed end,wherein the pressure sensing element is configured to measure fuelpressure within the pressure chamber; and a coil disposed within thehousing, wherein the coil is electrically connected with the pressuresensor, and wherein the coil is configured to generate a magnetic fieldresponsive to electrical signals from the pressure sensing element thatmoves the magnetic armature axially within the inner tube to controlfuel pressure by allowing fuel entering the pressure chamber via thefuel inlet passageway to exit via the fuel outlet passageway; and a fuelreturn line connecting the pressure regulating apparatus and the fueltank, wherein the fuel return line is configured return fuel exitingfrom the pressure regulating apparatus via the fuel outlet passageway tothe fuel tank.
 7. A direct injection fuel system according to claim 6wherein the inner tube further comprises: a radially extending flangeadjacent the inner tube open end; and an aperture formed through aportion of the flange, wherein the longitudinally extending channel inthe outer tube is in fluid communication with the fuel inlet passagewayvia the flange aperture and forms a fuel flow path between the innertube and the outer tube from the fuel inlet passageway to the pressurechamber.
 8. A direct injection fuel system according to claim 7 whereinthe fuel is pumped to a pressure of between about 0 psi and about 1,500psi.
 9. A direct injection fuel system according to claim 6 wherein theinner tube second end has an annular configuration.
 10. A directinjection fuel system according to claim 6 wherein the longitudinallyextending passageway in the magnetic armature comprises a longitudinallyextending slot formed in the outer surface of the magnetic armaturebody.
 11. A direct injection fuel system according to claim 6 whereinthe magnetic armature comprises a pair of diametrically opposedlongitudinally extending slots formed in the outer surface of themagnetic armature body.
 12. A direct injection fuel system according toclaim 6 wherein the body of the inner tube and the body of the outertube each have respective cylindrical configurations.
 13. A directinjection fuel system according to claim 6 wherein the pressure sensingelement comprises a semiconductor element that deflects in response to adeflection of the outer tube second end caused by fuel pressure withinthe pressure chamber.
 14. A direct injection fuel system according toclaim 13 wherein the semiconductor element comprises an embeddedWheatstone bridge.
 15. A direct injection fuel system according to claim6 further comprising means for adjusting axial movement of the magneticarmature within the inner tube relative to a magnetic field produced bythe coil.
 16. A direct injection fuel system according to claim 6further comprising a controller electrically connected with the pressuresensing element and configured to maintain fuel pressure within aprescribed range of pressures, and wherein the controller is selectedfrom the group consisting of proportional controllers, derivativecontrollers, integral controllers, proportional-derivative controllers,proportional-integral controllers, and proportional-integral-derivativecontrollers.